63super88

since a got the car, 63 S 88, I noticed a slightly uneven idle and a putting noise in the exhaust and a pinging when I get on the gas. I had figured it could be a vacuum leak or needs a mix adjustment but its defninately not those two because the line are all solid and the timing/dwell/idle mix is the best its gonnba get and I just still cant get it to idle smoothly.

I took the cap off the distributor and noticed one of the ends were a lot shinier than the rest, so I followed it to the #3 plug and pulled the plug which was very fouled after only 7000 mi when every other plug seems to be burning clean and just right, this plug was pretty caked like as if it hasn't been igniting at all while the others are hardly even blackened. I pull the wire off it while its running to see if it made a difference and it did slightly so I am not sure, how should I go about figuring out this cylinder because its definitely not right?

another strange thing I had seen was on an episode of Jay leno's garage he had a 59 super 88 and he described similar problems a miss or vacuum leak and had found that the mainb gasket between the top/bottom part of the 4bbl was incorrect and created a vacuum leak unnoticeable from the outside, is this a possibility and would this create the strange miss-like behavior? help please!

63super88

heres the link to that video, skip to 7:55 to hear jay explain the problem he had: sounds very similar to mine

oldcutlass

You need to make sure that cylinder is firing, replace the plug and possibly that wire. The ping may be to advanced timing.

63super88

Well the wire is definitely getting spark to the plug, it definitely sparks when I touched it with a test light. I set the gap at .30 like the manual said and the plugs are newish. When I unplug/ ground out the wire it definately changes pace so I think maybe its not dead completely its firing somewhat, what would make the cap wear out funny like that just that one is still shiny? When I saw that video I figured I could be having the same wrong-gasket issue as Leno's car is that worth looking into would it cause this as he described a similar misfire sensation?

MDchanic

Is there excessive wear to your distributor bushings?

- Eric

63super88

Im not sure, I mean its original but it doesnt have excessive mileage less than 91000 ive seen distributors that lasted 200,000, so it seems to be doing its job just fine. Its just that one line to #3 is funny and the motor idling with an uneven shake/ putting. Since I know that cylinder is getting spark yet still acting up where do I go from here? I dont have a compression tester er nothin, im really hoping its nothing internal

MDchanic

You've answered your own question.

With one crappy plug that seems to be working okay, you should check compression, and do a leakdown test if the compression is iffy.
You should also replace the plug and check it frequently to see what it looks like before it gets really icky.

Since you have evidence of the rotor possible striking one of the distributor terminals, you should check for looseness of the bushings, ideally be removing the distributor.

It is very possible that neither of these problems has any relation to the roughness you are experiencing, so once you have checked them out, you may need to continue troubleshooting.

- Eric

Charlie Jones

I really think that a compression check should be next. If you don't have a guage you may be able to borrow or rent one from an auto supply store.
Many major chains such as autozone have such a program.
Check compression with the coil wire disconnected and the throttle wide open.

MDchanic

And all spark plugs out.

- Eric

oldcutlass

You say the timing and dwell are the best they are going to be, what are they set to? When you set your carb did you use a vacuum gauge, or tach?

nsnarsk65cutlass

Jay Lenos problem was a carburator gasket problem not the same as yours,i'd do as others said compression and leak down test on the engine.

63super88

dwell is at 30.5 and the timing is at 5 degrees right in the center of the markings and that's the best it gets ive tried slightly advanced/declined it seems to run/start best when set exactlya to spec, and the idle screws are both set to between 3-3 1/2 turns out (I use a tac, but really i just go by how the car runs and smells because with the shaky misfire behavior its hard to get an even read on the tac anyway but im pretty sure that's about the normal mixture setting anyway right), so the car seems to like these settings best, ive been driving it every day for a year so ive tinkered with these adjustments quite a bit but I just cant get it to smoothly idle or this cylinder to behave. i don't think the bushings in the distributor are bad it all seems pretty tight not loose or funny at all so i doubt the rotor is actually hitting the actual point on the distributor the rotor itself doesnt seem bent but its probably old, its about time for a new one along with condenser and cap. also if there is an internal issue causing this im pretty sure it has nothing to do with valves because I took the valve cover off to change the gasket and it looked clean enough to eat outta there, all the arms looked tight and clean so its really leaning now towards problem in the cylinder which would really kill the enjoyment of this car, I don't feel like another engine pull project.

and the only reason I had thought at first that it was a carburetion problem was because it jus sounded like a crappy vacuum leak that I couldn't find, and id seen jay having the same problem describing an 'almost misfiring' sound but now I found this and said 'oh no, now Im wishing it was just a carburetor problem'

I guess im going to have to get my hands on a compression tester and test the cylinder with all the plugs out and unhooked coil so it doesn't start right, so what would holding open the throttle do? ive never done these tests before how would I perform that leak down test, get a tester plug it in fill the cylinder then what?

63super88

after watching some instructionals, I guess for the leakdown I gotta get it to top dead center closed valves, attach leakdown tester fill it to 45-55psi and listen through the carb/exhaust for air and check the rad for bubbles etc, and hold throttle open to hear for the intake leak and some guys said leave the plugs in for this one because sudden air pressure could make the engine turn suddenly idk what do you guys say? and how long should it take to empty, what is standard? how do these things usually go down?

and for the compression test just hook up tester to troubled cylinder, crank engine 3-4 times over with coil wire off and all plugs out, my old manual should tell me the spec for what it should read and if its low right? anything im forgetting? a link to a page with these specs would also be helpful

I found cheap testers but they come with 12 mm and 14mm adapters, I have to get an adapter that will fit this cars spark plug threads will one of these fit?

MDchanic

Holding the throttle open prevents the formation of a vacuum, which would defeat the purpose of testing compression.

You need a leak down tester (and an air compressor) to do a leak down test.
Not hard to come by, but treat it with care and follow the instructions.

- Eric

Don R.

All good suggestions, here are a few other things to check:

*Check resistance on that plug wire or substitute another wire, see if the idle clears up.
*Disconnect and plug vacuum line to the distributor advance can, does that help? If you have a blown diaphragm it causes a vacuum leak. (Ask me how I know!)
*Tighten carburetor base bolts.
*Even though you think your vacuum lines are all good there are a lot of connections under the dash that you can't see. Try disconnecting and capping each source line on the engine one at a time and see if you notice an improvement, if you do then check / replace all the lines that are fed from that source.

I had a similar problem with idle on my 63 without the plug issue and it took forever to track it down, in the end it was MULTIPLE vacuum leaks. Good luck!

63super88

well when it comes to vacuum leaks, the advance is def working (I timed the engine a few times so I would've noticed dead avance when I plugged it up then). the heat/ a./c control switches have lines that run to the actuators under the hood and all seem to be good (ive tried to follow them and check best as I can, and the buttons all activate fine) that's why I was thinking it was a hidden issue deeper inside the carb.

im hoping that when I change the cap, rotor and condenser and wires tomorrow it will help. im going to get a new set of champion plugs and leak down test the cylinder anyway. I just hope one of the cheap harbor freight tester's adapters fit the threads.

MDchanic

Should be no problem. They're very standard threads.

I would also recommend disconnecting and plugging ALL of the vacuum lines on the engine at the same time, to eliminate the possibility of small, cumulative leaks, as mentioned above.

- Eric

oldcutlass

Listen to where the air is escaping to see where your issue is if you have one. It will leak through the valve cover, the carb, or the exhaust.

MDchanic

Well, it will leak through the rings without a doubt, so you will hear some blowing by listening at the oil filler, but there should be none at the carb or the exhaust.

A calibrated leakdown gauge should tell you if the leakage into the crankcase is too much.

- Eric

Don R.

On my car I had split vacuum lines under the hood that looked fine until you touched them, TWO bad vacuum advance cans, and a leaking trunk release switch inside the car, all of which screwed up the idle and made it impossible to adjust. While all this was going on the heat / AC switches still worked. When I finally tracked all this down it ran like a new car. No matter what else you find check this out by isolating the engine vacuum sources and using a vacuum gauge.

oldcutlass

A leak down test can show leaks through the intake valve, you will hear air out the carb. It will also tell you if you have a bad exhaust valve by hearing air out the exhaust.

Ring leaks will come out the valve covers or the oil fill tube.